Photographic gelatin layer containing a monoester of sorbitol



Plantai 299, 194i GELATIN LAYER .CON-

PHOTOGHIG TG A MONOESTEE F SORBITOL Donald R. Swan, Bochester, N. Y., 'assiznor to Eastman K 00y, Rochester, N. Y., a corporation or New Jcmy ENT bil id No Drawing. Application March 2, 1940, Se No. 321,001

This invention relates to photographic lightsensitive materials, such as sensitized ,i 1 1m plates, and paper, comprising layers in which sensitive silver salts are suspended or dispersed in gelatin .fact, the spreading of any gelatin or other at" drophilic colloid layers which are deposited from a. predominantly aqueous medium and used in such photographic materials.

My invention perhaps finds its greatest usefulness in the manufacture of photographic film in which a sensitive gelatin emulsion layer is applied to the film base, set by chilling, and then, without drying, is overcoated with a. protective gelatin layer, the sensitive gelatin emulsion layer containing such a spree agent. 'llhe general process of coating Ii at base with a sensitive gelatin emulsion layer, setting by chilling, and overcoating with a protective gelatin layer, is

, fully set forth in U. S. Patent No. l,6$9,349 of William B. Daiiey.

If a sensitive gelatino-silver-halide emulsion is coated on a film base (which has usually first been coated. with a thin layer or sub-strat of gelatin or other colloid and dried) without the addition of a suitable spreading agent, on

culty is experienced in that the emulsion will spread unevenly. Moreover, if the emulsion while still in a wet, chilled condition. is overcoat/ed with a protective gelatin coating, air bubbles iorni between the emulsion layer and the protective layer. Either of these defects, of course, greatly impairs the uality of the photographic him.

It has, therefore, been customary in the art to add certain agents, such, for instance, as saponin, to the'sensitive emulsion in order to avoid these defects as far as possible. Sanin has'surface-active properties, and not only acts as a spreading agent for gelatin, but by some mechanism not clearly understood, it prevents the formation of air bubbles between the gels layers when a wet, chilled gelatin emulsion layer containing the proper concentration of saponin is overcoated with a warm gelatin solution.

However, saponin, being a naturally occurring material of vegetable origin, is of varying quality, and synthetic agents are to be preferred because of their more constant and controlled properties. Because of its varying quality, some batches of saponin may cause an incre in log or a decrease in sensitivity in the sensitive emulsion, and in some cases may produce little or no improvement in spreading. This is true whether the saponln be employed in the emulsion layer or in the protective overctins or other layer.

Othersurface-active materials have been tried in place of saponin, but many of them, while they may act to some extent as spre agents for gelatin, have been found to be entirely inedective for preventing the lotion of air bubloles when a wet, chilled gelatin emulsion con taining them is over'coated with a warm gelatin solution, and many of them are objectionable from the stdpoint of logging or desensitiainu the emulsion.

i have found a class of suriace active compounds which are not only excellent spreading ents iorgelatin and other hydrophilic colloid layers which are deposited from a predominantly aqueous medium andused in photographic films, plates, and paper, but which, when dispersed in layers such as sensitive gelatin emulsions, prevent the formation of air bubbles when the wet, chilled emulsion layer is overcoated with a warm gelatin solution or other hydrophilic colloid of the type which is deposited from a predominantly aquwus medium. These compounds are the monoesters of sorbitol with an acid selected from the group consisting of the aliphatic acids of from 8 to 18 carbon atoms and the alicyclic acids. They no he prepared by the partial esterlilcationof sorhitol in pyridine by the acid chloride, in the manner described in U. S. Patent l lo. 1,959,930 of Otto Schmidt, Example 2. lndivld uni acid chlorides may be used, such as the chicrides oi laurlc, myristic, oleic, rlcinoleic, napln thenio, aloietic or hydroabietic acid, or the chlorides oi the mixture of acids obtained from coconut oil may be used. 0f the aliphatic acids, lauric acid and the mixture of coconut oil acids are prelei-red.

These sorbitol monoesters are not suficiently water-soluble to remain for ions in a fluid gelatin or similar emulsion. Therefore, it is necessary to disperse them in the gelatin emulsion by means of some oer-soluble dispersing agent, such, for instance, as sodium lauryl B-suifobutyrate, sodium lauryl sulfonate, sodium B-oleyl 1"; doethyl sulfonate, sodium B ladoethyl sullate, etc. The mixture of sorbitol monoester and dispersing agent may be incorporated in the sen sitive gelatin emulsion at any point in its iacture such thatit will present during the coating oi the emulsion, in the proportion of irom 0.001 to 0.002 part of sorbitol monoester and from 0.02 to 0.04 part of the dispersing agent per 100 parts by weight of wet emulsion. This gives a a sorbitol monoester content of ,0.0i%-to 0.02% d a content of disng agent or 0.2% to 0.0%

in the dried emulsion layer. These sorbitol monoshow higher speed and less fog after prolonged storage at elevated temperatures than ordinary iilm stored for the same'length of time under the same conditions. They are also more readily wet by the developing solution.

It is believed that the property oi the spreading 1 agent which prevents the formation of air bubbles when a wet, chilled gelatin emulsion is overcoated with a m gelatin solution, also tends to prevent the iormation of air bubbles, repellent spots, etc., on the surface of a sensitive'emulsion containing such a spr agent, when that emulsion, coated on a film, plate, paper, etc., is immersed in a developer.

As above pointed out, the dispersed sorbitol monoesters defined may be used in any one or more of the colloid layers used to build up a photographic sensitive element upon a base such as him, glass, paper, etc., which layers consist of i. e., a medium used as the solvent for such materials in which water predominates, the remainder. oi the medium contributing to give a good dispersion of the colloid. If two superposed colloid layers are present, either, neither or both of which may be photographically sensitive, the

spreading agent may be used in either layer or in both layers. However, where a wet, chilled light-sensitive gelatin or similar layer is to be overcoated wit a warm solution-or emulsion of gelatin or slmi or material, the presence of the spreading agent in the wet, chilled layer is essential for preventing the formation of air'bubbles between the layers. Examples of such hydrophilic colloids other than gelatin, which are useiul as layers in photographic films, plates, paper, etc., are the water-soluble cellulose derivatives such as well hydrolyzed cellulose acetate (described ln U. 8. Patent No. 2,110,491 of $8.10) and cellulose esters of hydroxy monocarboxylic acids,

attests .philic colloid depcsitable from a predominantly aqueous medi is referred to, it will be understood to mean hydrophilic colloid which can be deposited'irom a medium which is predominantly aqueous, the remainder oi! the medium being an organic solvent which contributes to the dispersibility of the colloid: examples of such org'anic solvents for this purpose are acetone, ethyl alcohol, ethylene glycol, monoacetin and pyridine.

secured by Letters Patent oi the United States is:

gelatin or other hydrophilic colloid which is deposited from a predominantly aqueous medium,

from 0 to 18 carbon atoms and the alicyclioacids. 2. Photographic sensitive material comprising a gelatin layer containing in a dispersed state from 0.01% to 0.02% o! a monoester of sorbitol with an acid selected irom the group consisting of the aliphatic acids oil from 8 to 18 carbon atoms and the alicycllc acids.

3. Photographic sensitive material comprising a base and two superposed gelatin layers in,

which the gelatin layer nearer the base contains, in a dispersed state, from 0.01% to 0.02% or a monoester of sorbitol with an acid selected from the group consisting of the aliphatic acids of from B'to 18 carbon atoms and the alicycllc acids.

4. Photographic sensitive material comprising a base, a photo-sensitive gelatin emulsion layer contains, in a dispersed state, from 0.01% to 0.02% of a monoester oi" sorbitol with an acid sesuch as lactic or glycollic, and salts of cellulose esters of dicarboxyllc acids, such-as phthalic (described in U. S. ,Patent No. 2,127,573 of Sheppard and U. 8. Patent No. 2,127,621 of Stand), as well as polyvinyl alcohol and hydrolyzed polyvinyl acetate (described in applications of Wesley G.

Lowe, Serial Nos. 318,559v and 318,560, filed Feb-.

= lected from the group consisting of the aliphatic 7. Photographic sensitive material comprising a gelatin layer containing, in a dispersed state, from 0.01% to 0.02% 01' sorbitol mono-hydroabietate.

DONALD E. SWAN.

, it may be desirable to cost them' I claim as my invention and desire to be 

